Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-08-29
2001-11-27
Vu, Huy D. (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S404000
Reexamination Certificate
active
06324180
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a local area network operating in the asynchronous transfer mode (ATM) for transmitting cells, comprising a plurality of network interfaces coupled to a ring by ring connections, each network interface including a switch.
A local area network (LAN) operating in the asynchronous transfer mode is known from EP-0 641 105 A2. This network comprises a plurality of network interfaces which include each a transmit and a receive terminal, and stations coupled to the network interface by wires. Cells containing information about the destination, for example, of a certain station are transmitted by the ring formed in this manner. A network interface comprises a switch and a controller. The switch contains respective path memories which are assigned each to a receive connection. When a cell is received, the switch performs switching or coupling operations instructed by the switch modes based on the stored paths. For example, an incoming cell is transferred to the controller, to the station and/or to the ring. The controller is, for example, charged with connection set-up and disconnection operations.
When an asynchronous transfer mode is used in a system, payload information such as telephone, picture or sound signals are transmitted in fixed-length blocks via digital signal processing arrangements. A cell having a predetermined number of bytes (for example, 53 bytes) is denoted a fixed-length block. Each cell comprises a header field having a length of, for example, 5 bytes, and an information field in which the payload information is accommodated having a length of, for example, 48 bytes. In such a header field are contained address information, data for error detection and data for control indication bytes. Address information comprises a trunk identifier which is referenced VPI (Virtual Path Identifier), and a link identifier which is referenced a VCI (Virtual Channel Identifier). VPI and VCI together denote a virtual link or a virtual channel. A group of a plurality of virtual channels is denoted a virtual path, featured by the trunk identifier.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a flexible local area network operating in the asynchronous transfer mode.
The object is achieved by an asynchronous transfer mode local area network of the type defined in the opening paragraph, in that at least one network interface comprises a radio device for exchanging data with at least one terminal situated in the radio coverage area of the network interface, and in that the switch is provided for transporting the cells at least between ring connections and the radio device.
According to the invention, one or more network interfaces include a radio device coupled to one or more terminals by a radio link. Certain other network interfaces may be connected to stations or other networks by wired connections. The network interfaces are then combined to a ring by one or a plurality of ring connections. The cells (ATM cells) available for radio transmission in a network interface or a terminal are given control indication bytes and additional information and sent to the radio link as one packet unit. The packet unit may then be part of a cell, a complete cell or a plurality of cells. Methods that may be used for radio transmission may be, for example, TDMA, FDMA or CDMA methods (TDMA=Time Division Multiple Access; FDMA=Frequency Division Multiple Access; CDMA=Code Division Multiple Access). The methods may also be combined, as appropriate. For example, a certain carrier frequency may be assigned to a network interface and to the terminals located in the radio coverage area of the network interface. The radio transmission between a network interface and the terminals may then be effected according to the time-division multiple access method.
The cells received in a network interface from the radio device or from the ring are transferred by the switch to the ring and/or to the radio device and/or to the control circuit. Signaling cells which are responsible, for example, for the connection set-up and disconnection, and user cells containing user information for an existing connection are then transferred. There are two types of cells available: a signaling cell and a user cell.
According to the invention, it is thus possible that various terminals are located in the radio coverage area of one network interface. They can be connected and disconnected at will, without further costly wired connections being provided, so that the local area network becomes flexible to the user. A user is, for example, a user of a program in a terminal, a program itself, stored data (terminal as a data bank), or a telephone user.
Each switch of a network interface includes a receive circuit assigned to a receive connection, which circuit evaluates the header field of a received cell. Based on the information from the header field, a receive circuit takes a switch mode from the assigned path memory arrangement.
Switch modes for various virtual links can be stored in the path memories. Six switch modes are provided for the path memories coupled to the radio device. A first switch mode is provided for a connection at least between two local terminals, in which mode the switch couples the receive and transmit connections connected to the radio device. A second switch mode is used for a connection at least between a local and a remote terminal, in which mode the switch couples the receive connection connected to the radio device and one transmit connection connected to a ring. A third switch mode is used for providing a connection between at least two local and at least one remote terminal, in which mode the switch couples the receive connection connected to the radio device to the transmit connection connected to the radio device and to a transmit connection connected to a ring. A fourth switch mode is used for a connection between a local terminal and the local controller, in which mode the switch couples the receive connection connected to the radio device to the local controller. A fifth switch mode is used for a connection between a local terminal and the local and at least one remote controller, in which mode the switch couples the receive connection connected to the radio device to the local controller and a transmit connection connected to a ring. In the sixth switch mode, cells containing non-existing connections are deleted.
The switch modes for a virtual link are stored during the connection set-up. A switch mode for a virtual link is stored in a path memory by the respective controller, The path memory is then provided for storing the type of connection, the type of cell and the switch mode while a virtual link is featured. The virtual link is featured by the combination of the VCI (Virtual Channel Identifier) and VPI (Virtual Path Identifier) contained in the header field of a cell. The type of the connection indicates whether a unicast connection i e. point-to-point connection, a multicast connection i.e. point-to-multipoint connection or broadcast connection is concerned.
A terminal includes, as does a network interface, a radio device with a radio frequency circuit, a modem and a protocol device. The radio device of a terminal exchanges data with the radio device of the associated network interface. A terminal transmits identification data by a recording channel, MAC signaling data (MAC=Medium Access Control) by a MAC signaling channel and payload information by at least one transport channel. The payload information contains at least part of a cell. The network interface informs the terminal by the MAC signaling channel, for example, the transport channel or channels appropriate for the transmission of payload information.
A network interface in the local area network has an additional object. It is the control of the connection set-up and disconnection of each virtual link. When a user wishes to have a connection to another user, this network interface verifies whether this is feasible.
The i
Boakye Alexander O.
Thorne Gregory L.
U.S. Philips Corporation
Vu Huy D.
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